215/45 R18 doesn't belong to the most popular dimensions for tyres - there are tyre models available, which can be compared to
325/30 R21,
155/60 R15,
155/65 R13. Let's break down the sizing - 45 is height of the tyre, which is calculated as 45% of the tyre width (215mm), which means the sidewall height has 96.75 mm. The wheel diameter is R18, which means it fits to a 18 inch/457.2mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 165/65 R15
(1870.82 mm), 245/50 R19
(2285.82 mm), 175/60 R15
(1856.68 mm), 255/30 R19
(1996.8 mm), 180/55 R17
(1978.58 mm), 255/40 R20
(2236.81 mm), 185/60 R15
(1894.38 mm).
